VITAL PRINCIPLE. 27 



rals abound, while there are few examples of petrified fish. 

 In the more recent strata, the remains of reptiles, birds 

 and quadrupeds, occur, all of them differing from the 

 existing kinds. 



Attempts have been made to account for these circum- 

 stances by supposing, that the present races of animals and 

 vegetables, are the descendants of those whose remains 

 have been preserved in the rocks, and that the difference 

 of character may have arisen from a change in the physL 

 cal constitution of the air, or the surface of the earth, 

 producing a corresponding change on the forms of orga- 

 nized beings. The influence of cultivation on vegetables, 

 of domestication on animals, and of climate on man him- 

 self, may be considered as strengthening the conjecture. 

 But there are several difficulties which present themselves 

 to those who adopt this opinion. The effect of circum- 

 stances on the appearance of living beings, is circumscri- 

 bed within certain limits, so that no transmutation of species 

 was ever ascertained to take place ; and it is well known, 

 that the fossil species differ as much, nay more, from the 

 recent kinds, as these last do from one another. It re- 

 mains, likewise, for the abettors of this opinion, to connect 

 the extinct with the living races, by ascertaining the inter- 

 mediate links or transitions. This task, we fear, will not 

 be executed speedily. 



There is yet another view of the matter which suggests 

 itself. If the seeds of some plants, and the eggs of certain 

 animals, be so minute as to be excluded with difficulty 

 from any place to which air and water have access, and if 

 they are capable of retaining, for an indefinite length of 

 time, the vital principle, when circumstances are not fa- 

 vourable to its evolution, the crust of the earth may be 

 considered as a mere receptacle of germs, each of which is 

 ready to expand into vegetable or animal forms, upon the 

 occurrence of those conditions necessary to its growth. 



